Conventional film-form seating detection switches are known which are capable of detecting when a person has sat down in a seat, disclosed in for example Japanese Unexamined Patent Publication No. 9-315199 and Japanese Patent Publication No. 2909961. Such conventional seating detection switches comprise one electrode fixed to one surface of one film of a pair of films, electrically connected via one wire, another electrode fixed to the surface of the other film of the pair of films opposing the surface of the first film, electrically connected via one wire, and a spacer arranged between both those films such that these two electrodes are normally separated and in mutual opposition. In this arrangement, if a person sits down in a seat on which such a seating detection switch is disposed, the opposing electrodes come into contact thereby becoming conductive, in response to the weight of the sitting person.
FIG. 1 is a schematic view of the structure of a conventional seating detection switch 300. FIG. 2 is a cross-sectional view of the seating detection switch 300 of FIG. 1 along the line II-II.
As shown in FIG. 2 this conventional seating detection switch 300 comprises an insulating, film-form spacer 304 interposed between a film-form substrate 302 arranged on one of the surfaces of the spacer 304 and a film-form member 306 arranged on the other surface of the spacer 304.
This conventional seating detection switch 300 is used arranged at the rear side of the surface covering of a seat in which a person can sit down. This switch 300 is thus used as a seating detection device that operates in response to the body weight of a passenger that sits down in the seat to detect whether or not the passenger is seated in the seat.
FIG. 3 is a schematic view of the structure of the film-form substrate 302 forming the conventional seating detection switch 300. As shown in FIG. 2 and FIG. 3, on the surface of the film-form substrate 302 facing the film-form member 306 (the inner side surface), a plurality of contact points 308A-308D are each disposed mutually separated, in order to detect the seating of a passenger in the seat.
As shown in FIG. 3, these contact points 308A-308D are electrically connected to each other via a conductive wire (conduction route) 310 that is wired on the inner side surface. A first terminal 312 is disposed at one end of the wire 310, acting to connect this conventional seating detection switch 300 to another electronic device (for taking signals from the seating detection switch).
The wire 310 is disposed separating into a plurality of branches in the direction moving away from the terminal 312. Each of the contacts 308A-308D are disposed over the wiring, extending along the wiring branches (refer to FIG. 3).
FIG. 4 is a schematic view of the structure of the spacer 304 forming the conventional seating detection switch 300. This spacer 304 is of the same form as the film-form substrate 302 and provides a plurality of openings 320A-320D. Each of these openings 320A-320D is disposed in a position that corresponds to the respective positions at which the contacts 308A-308D are disposed.
FIG. 5 is a schematic view of the structure of the film-form member 306 comprising a conventional seating detection switch 300. This film-form member 306 is of the same form as the film-form substrate 302. A plurality of contacts 314A-314D that correspond to each of the contacts 308A-308D and each of the openings 320A-320D are disposed on the surface of the film-form member 306 facing the film-form substrate 302 (the inner side surface). Further, on that inner side surface in the same manner as the film-form substrate 302, are disposed a conductive wire (conduction route) 316 and a second terminal 318 for taking signals from the seating detection switch (refer to FIGS. 2 and 5).
FIG. 6 is a circuit diagram of the conventional seating detection switch 300. The contacts 314A-314D and the corresponding contacts 308A-308D are normally spaced apart by the spacer 304. When a passenger sits down in the seat, the film-form substrate 302 and film-form member 306 bend, the contacts 314A-340D and the corresponding contacts 308A-308D (for example contact 308A to contact 314A) contact each other, and the first terminal 312 and second terminal 318 enter a condition of mutual electrical conduction (in other words, they are connected), thereby enabling the seating of the passenger to be detected.
In the conventional seating detection switch the surface on which one of the electrodes is formed is taken as the front surface and the surface on which the other electrode is formed is the rear surface. One of the terminals connected by an electrical wire to one of the electrodes is disposed on the front surface of this conventional seating detection switch, while the other terminal connected by an electrical wire to the other electrode is disposed on the rear surface of this conventional seating detection switch.
In this way, as one of the terminals is disposed on the opposite surface to the other terminal, after a connection terminal of an electrical wire provided by a wiring harness or the like is connected to one of the terminals, it becomes necessary, in the case of this conventional seating detection switch, that the switch be turned over to enable a connection to be made to the other terminal. Thus, a problem arises in that it is troublesome to connect a connection terminal of an electrical wire (signal wire) provided by a wiring harness to each of the terminals.
Further, when a conventional seating detection switch is installed for example on a seat and a person sits down in the seat, a part of the conventional switch (e.g. the part in the vicinity of the seat back of the seat) is substantially curved.
As the conventional seating detection switch has a triple layer construction consisting of a film pairing with a spacer disposed therebetween, significant stress arises inside the seating detection switch in the parts subject to such curving and this may cause the switch to sustain damage.
Moreover, the conventional seating detection switch 300 is configured such that in any single contact pairing comprised of the contacts 308A-308D with the corresponding contacts 314A-314D (e.g. the contact pairing formed by contact 308A and 314A), if the opposing contacts of the pair come into contact with each other the first terminal 312 and second terminal 318 enter a condition of electrical conduction.
Accordingly, a problem arises due to concern about the switch incorrectly detecting that a person has sat down in the seat if for example the edge of some luggage is positioned over a single contact pairing causing the contacts of that contact pairing to come into contact with each other, even though a person has not actually sat down in the seat.